Calls have been made for a specialist mother and baby mental health unit to be reinstated in Wales.
Mind Cymru said some mothers needed support travel for at least three hours to England after Wales’ last unit closed in Cardiff in November 2013.
Plaid Cymru AM Steffan Lewis called the situation a “scandal”.
The Welsh Government said it was “vital” to offer support during pregnancy and pointed to existing community services.
Mother and baby units (MBUs) provide specialist care to women with mental health problems such as severe postnatal depression and postpartum psychosis.
Speaking ahead of Mother’s Day on Sunday, mental health charity Mind Cymru said 10-15% of new mothers developed postnatal depression, which usually develops within six weeks of giving birth and can come on gradually or suddenly.
Senior policy and campaigns officer Rhiannon Hedge said: “With no support here in Wales, mothers are having to be treated many miles away from their families and support networks.
“While community support is important, there are times when specialist in-patient care is necessary and at those times it’s simply not appropriate for women to be so far away from their families.”
She said money invested into community perinatal support was welcome but the Welsh Government’s delivery plan, Together for Mental Health, “doesn’t go far enough in addressing the gaps”.
In Cardiff and Vale health board area alone, 21 women between January 2015 and January 2017 were identified that would have been admitted to the Welsh MBU had it been open.
The figures, obtained by Mr Lewis through the assembly research service, showed of six women who were referred to an out-of-Wales MBU in that time, only two went because others did not want to be so far from their families.
A Freedom of Information Act request also found that the body that commissions specialist NHS services, the Welsh Health Specialist Services Committee (WHSSC), estimated that the cost of sending mothers to MBUs outside of Wales was estimated to be £377,000 this year.
But a paper by Cardiff and Vale University Health Board said £307,000 was released following the closure of the MBU.
Mr Lewis said there was “a clear demand in Wales for perinatal services in this country” and said the closure “hasn’t been cost effective”.
“This is a scandal that in this country that there are people who have real mental health needs and are not able to have those needs fully met here in this country,” he added.
‘Vital for families’
Charlotte Harding, from Cardiff, developed postpartum psychosis four years ago following the birth of her son. Symptoms can include high mood, racing thoughts, depression, severe confusion and paranoia.
She said: “Families in Wales are left to take care of mothers with severe postnatal depression by themselves. My husband had to take two years off work to look after me and our boys.
“Having a mother and baby unit in Wales is vital for families but even more important for single mothers facing mental health problems alone.”
A Welsh Government spokesman said the previous MBU was closed due to an insufficient number of women using the service to enable staff to maintain skills, “not funding issues”.
She added: “Last year, we announced new perinatal mental health services will be set up within every health board in Wales, backed by £1.5m of new investment.
“The new community-based specialist services will help to improve mental health outcomes for women with perinatal illnesses, their babies and their families.
“The NHS reports more than 1,500 women have been referred to the new community services since April 2016 and we expect the figures to increase significantly as services are established.”
He said it was “very rare indeed” for a mother to need to be admitted to hospital with her baby, but in those circumstances the WHSSC worked with local services to find a bed “as close to home as practical”.
The WHSSC will report on its inpatient service provision in the near future, she added.